Production of heavy actinides from interactions ofO16,O18,Ne20, andNe22withCm248

Abstract

We have measured cross sections for the production of isotopes of Bk through No in bombardments of $^{248}\mathrm{Cm}$ with $^{16}\mathrm{O}$, $^{18}\mathrm{O}$, $^{20}\mathrm{Ne}$, and $^{22}\mathrm{Ne}$ ions at energies near the Coulomb barrier. In general, the peak of the mass-yield curve for each element is about two mass units larger for $^{18}\mathrm{O}$ and $^{22}\mathrm{Ne}$ than for $^{16}\mathrm{O}$ and $^{20}\mathrm{Ne}$, reflecting the neutron excess of the projectiles. The production cross sections and maxima of the actinide isotopic distributions are at least as favorable for production of neutron-rich actinides as those measured for irradiation of $^{238}\mathrm{U}$ and $^{248}\mathrm{Cm}$ with very heavy ions. The observation of so many neutron-rich products between the masses of the target and compound nucleus suggests a direct transfer reaction in which the product nuclide is formed with relatively low excitation which minimizes depletion from prompt fission.NUCLEAR REACTIONS $^{248}\mathrm{Cm}$($^{16,18}\mathrm{O}$,$X$), ($^{20,22}\mathrm{Ne}$,$X$) $E(^{16,18}\mathrm{O})=98, 97$ MeV, $E(^{20,22}\mathrm{Ne}=115, 116 \mathrm{MeV})$; measured $\ensuremath{\sigma}$ and isotopic distributions for $Z=97\ensuremath{-}102$.